Blind fastener and drive nut assembly

ABSTRACT

A blind fastener with an improved drive nut and assembly process. The blind fastener includes a screw, a sleeve, a nut, and a drive nut. The drive nut has a smooth bore and protruding nibs that mate precisely with a driving recess located in the nut head. A retaining device is used to retain the drive nut on the screw against the nut. Once the new assembly process for the blind fastener has been completed, the drive nut will have been mated with the nut head to prevent any rotation of the nut during installation of the blind fastener. The assembly process will now include placing the sleeve over the threads of the screw to a position adjacent the screw head. The nut is then threaded onto the screw adjacent the sleeve. The drive nut&#39;s protruding nibs are next aligned and physically engaged into the driving recess of the nut head by sliding the smooth bore over the screw. A retaining device is placed over the screw adjacent the drive nut to retain the drive nut to the screw. The retaining device can be an adhesive.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/825,711 filed Apr. 4, 2001, which claims priority fromProvisional application Ser. No. 60/232,336 filed Sep. 13, 2000.

BACKGROUND OF THE INVENTION

This invention relates to blind fasteners for securing panels and sheetmaterial together, and more particularly, to an improved drive nutassembly.

Blind fasteners are commonly used to secure two sheets together when itis otherwise impossible to access the underside (blind side) surface ofone of the sheets. Such fasteners have wide application in aircraft andspace vehicle assembly. Due to the vibrations and sonic fatigueencountered in these environments, it is necessary to create a fastenerof enduring strength and reliability.

The previously available blind fastener that this invention improvesupon comprises: (1) a screw, (2) a sleeve, (3) a nut, and (4) a drivenut. Examples of the previously available blind fasteners are disclosedin U.S. Pat. Nos. 4,772,167 and 4,747,202. Generally, the screw has anexternally threaded surface that allows the sleeve, the nut, and thedrive nut, which are each internally threaded, to be placed onto thescrew. The blind fastener is inserted into aligned apertures of thesheets that are being secured together, and after installation iscomplete the sleeve and the nut will clamp the sheets together.

The screw has the shape of a long threaded bolt with an enlarged head atone end of the screw, and at the end opposite of the head is twomachined flats. The machined flats are wrenching surfaces that allow atool to rotate the screw during assembly and installation of the blindfastener. The screw also has a frangible groove at a predescribedposition on the threaded section that is machined to a diameter smallerthan the minor diameter of the external thread. The purpose of thisfrangible groove is to prevent over torquing and/or excessive upsettingof the sleeve during installation by serving as a breakneck. When acertain installation load is achieved, the frangible groove preventsoverloading by failing first in torsional shear and then breaking awayfrom the assembly.

The sleeve has a cylindrical shape and is made of a malleable material.The purpose of the sleeve is to expand radially and abut against theblind side surface of the sheet during installation. The nut has acylindrical shape and resembles a flush head or protruding head bolt,with the exceptions that it is internally threaded throughout, and onthe top of the head has a driving recess. Further, the nut is dimpledaround its diameter in such a manner as to provide friction on the screwto prevent unloosening of the screw once the fastener is installed.

The driving nut resembles a traditional hexagon nut and has the sameinternal threading as the nut. On one end of the drive nut is achamfered angle that begins from the external hexagon shape and ends ata predetermined counterbore that is larger than the internal threaddiameter. Further, the drive nut has an annular ridge that is made of amalleable material that allows deformation of the annular ridge into thehead and the recess of the nut.

The assembly process of the previously available blind fastener consistsof the sleeve being placed over the screw until it abuts the head of thescrew, followed by the nut being threaded onto the screw until it isseated against the sleeve. The nut is then dimpled on the outer wall bya physical deformation process that places some of the nut materialagainst the internal screw to prevent loosening. The drive nut is thenthreaded onto the screw until it is seated against the head of the nut.The installation process of the blind fastener is accomplished by use ofa tool adapted to hold the drive nut stationary and simultaneously fitover the machined flats on the screw. The tool prevents the drive nutfrom rotating, while at the same time rotates the screw. As the screwrotates, the sleeve is pulled towards the blind side of the sheetmaterial. The malleable sleeve then abuts the sheet material and beginsto deform into an expanded diameter. Meanwhile, at the opposite end ofthe blind fastener assembly, the annular ridge of the drive nut beginsto deform and flatten against the nut head. As the torsional andcompressive load increases, the annular ridge of the deformable drivenut begins to rotate as much as 180° degrees before it penetrates therecess of the head of the nut which is evidenced by head marking andmaterial smearing.

The drive nut behaves as a “jam nut” by forcibly deforming against thenut head to prevent the nut from rotating. At a certain torsional andcompressive load the screw stops rotating and the breakneck frangiblegroove fails, causing the drive nut and remaining screw to fall away.

The problems with the presently available blind fastener derive from thedeformable drive nut. Optimum installation performance and reliabilityare not achieved from the blind fastener because the deformable drivenut allows undesired rotation and “jam nut effect”. The deformable drivenut rotates upon the head of the nut as the annular ridge of the drivenut deforms into the recess of the nut head. This deformation processcauses rotation of the nut and smearing or scraping of the nut head.This result is not only visually apparent, but can also deteriorate thenut's corrosion resisting properties and damage the plating under thehead and grip area of the nut. Finally, the “jam nut effect” of thedeformable drive nut causes large variations in the requiredinstallation loads. This can result in premature screw break off andinconsistencies in the amount of sleeve material that deforms into anexpanded diameter, thus compromising the integrity of the blindfastener.

Consequently, a need exists for a blind fastener with a non-deformabledrive nut that has positive engagement into the head of the nut therebyeliminating rotation of the nut and all of the problems associated withundesired rotation and “jam nut effect”.

SUMMARY OF THE INVENTION

The present invention is directed to a blind fastener with an improveddrive nut and assembly process. The blind fastener of the presentinvention includes a screw, a sleeve, a nut, and a drive nut. The screw,the sleeve, and the nut of this blind fastener are similar to those ofthe previously available blind fastener discussed above. Theimprovements of the present invention relate to a new structure for thedrive nut and a new assembly process for the blind fastener. The newdrive nut and assembly process significantly improve the reliability ofthe blind fastener by eliminating the inconsistencies associated withforcibly deforming the drive nut into the head of the nut.

The new drive nut of this invention has protruding nibs that mateprecisely with a recess located in the nut head. The protruding nibs ofthe new drive nut are not deformable and serve to replace the deformableannular ridge that was used in previous drive nut assemblies. Theconfiguration of the protruding nibs and the recess in the nut head canbe of many forms, so long as both parts are capable of being mated. Theprotruding nibs are fabricated at one end of the drive nut and areperfectly engaged to resist any installation torsional loading. Thedrive nut has an internally threaded bore to matingly engage the screw,or in an alternative configuration can have a smooth bore for placementover the screw. For smooth bore configurations the drive nut is held inplace on the screw by a retaining ring, insert or plug positioned on thedrive nut opposite the protruding nibs. Alternatively the drive nut canbe held onto the screw by an adhesive. Once the new assembly process forthe blind fastener has been completed, the drive nut will have beenmated with the nut head to prevent any rotation of the nut duringinstallation of the blind fastener into the sheets being secured.

The assembly process of the blind fastener comprising the new drive nutalso differs from that previously utilized. The assembly process willnow include placing the sleeve over the threads of the screw to aposition adjacent the screw head. The nut is then partially threadedonto the screw until the internal threads within the region of theenlarged nut head have not been completely threaded onto the screw. Foran internally threaded drive nut, the drive nut's protruding nibs arenext aligned and physically engaged into the mating recess in the nuthead. The mated drive nut and nut are next rotated which results in thedrive nut and nut being physically locked together and being threadedonto the screw as a single unit. Once the nut is adjacent to the sleeve,the assembly is completed by positioning the screw, the sleeve, the nut,and the drive nut so the nut can be dimpled. The dimpling process placesa small physical deformation on an outer surface of the nut whichdisplaces a small portion of the nut material against the internal screwto cause sufficient friction to prevent loosening.

For a smooth bore drive nut, the nut is threaded all the way onto thescrew adjacent the sleeve. The drive nut is then slid over the screwuntil the nibs engage the recess in the head of the nut. The drive nutis held in place by placing the retaining ring, insert or plug on thebackside of the nut, or alternatively by applying on adhesive into thesmooth bore.

Once the new assembly process is complete, the blind fastener having thenew drive nut is installed into the sheets to be secured by meanssimilar to those used with the previously disclosed blind fastener.Namely, a tool with a means for holding the drive nut stationary, and atthe same time rotating the screw, is used to cause the sleeve to deformagainst the blind side surface of the sheet and secure the sheetsbetween the nut and the sleeve.

As the sleeve deforms against the blind side of a sheet duringinstallation, the drive nut will not deform into the nut head. Themating connection between the drive nut and nut head prevents smearingand scraping of the nut head and preserves its corrosion resistantproperties. Unlike the previously available drive nut having adeformable annular ridge, the drive nut of this invention has no “jamnut effect”. The protruding nibs on the drive nut eliminates theunpredictability of installation loads placed on the screw by notforcibly deforming against the nut head. This in turn greatly reducesthe risk of premature screw break off and increases consistency in theamount of sleeve material that will be deformed against the sheet. Thesenew drive nut designs improve the consistency of loading by at least 30percent or more. This relates to a significant improvement inreliability of the installation process and reduces variability.

Other objects, features and advantages of the invention will be apparentfrom the following detailed description taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional side view of a first embodimentblind fastener system of the present invention;

FIG. 2 is a partial cross-sectional side view of the blind fastenersystem of FIG. 1 shown the drive nut engaged in the driving recess ofthe nut;

FIG. 3 is a partial cross-sectional side view of the blind fastenersystem of FIG. 1 showing the blind fastener after assembly is complete;

FIG. 4 is a partial cross-sectional side view of the blind fastenersystem of FIG. 1 showing the blind fastener during installation into apair of sheets;

FIG. 5 is a partial cross-sectional side view of the blind fastenersystem of FIG. 1 showing the blind fastener during installation into apair of sheets and the deformable sleeve has deformed;

FIG. 6 is a partial cross-sectional side view of the blind fastenersystem of FIG. 1 showing the blind fastener after installation iscomplete;

FIG. 7a is a top view of the nut of the blind fastener system of FIG. 1,showing the driving recess in a cross-slot configuration;

FIG. 7b is a partial cross-sectional side view of the nut of FIG. 7a;

FIG. 8a is a top view of the nut of the blind fastener system of FIG. 1,showing the driving recess in a single slot configuration;

FIG. 8b is a partial cross-sectional side view of the nut of FIG. 8a;

FIG. 9a is a perspective view of the drive nut of the blind fastenersystem of FIG. 1, showing four nibs having an angled engaging surface;

FIG. 9b is a perspective view of the drive nut of the blind fastenersystem of FIG. 1, showing four nibs having a flat engaging surface;

FIG. 10a is a perspective view of the drive nut of the blind fastenersystem of FIG. 1, showing two nibs having an angled engaging surface;

FIG. 10b is a perspective view of the drive nut of the blind fastenersystem of FIG. 1, showing two nibs having a flat engaging surface;

FIG. 11 is a cross-sectional view of a second alternative embodimentdrive nut and retaining device; and

FIG. 12 is a cross-sectional view of a third alternative embodimentdrive nut and retaining device.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is embodied in a blind fastener 10, for use inconnecting two or more panels or sheet materials together. Typically,the sheets are made of materials commonly used in the aerospace industryincluding aluminum or other composite materials. As shown in FIG. 4, theblind fastener 10 is designed to create a clamping force thereby holdingsheets 12 and 14 together. The blind fastener 10 is particularly usefulin the assembly of aircraft and space vehicles where access to theinaccessible or “blind” surface 18 of sheet 14 is not possible.

Referring to FIG. 1, the blind fastener 10 includes a screw 20, a sleeve30, a nut 40, and a drive nut 50. Generally, the screw 20 has externalthreads 22 which allow the sleeve 30, the nut 40, and the drive nut 50to be placed onto the screw 20. At this point, the blind fastener 10 isassembled and installed into the sheets 12 and 14, which each haveapertures of a diameter large enough to allow insertion of the blindfastener 10 into the sheets.

The screw 20 has the shape of a long threaded bolt with external threads22 and an enlarged head 24. At the end opposite of the enlarged head 24is two machined flats 26 which provide wrenching surfaces that allow adriving tool (not shown) to engage the machined flats 26 and applytorque resulting in rotary movement of the screw 20. In a preferredembodiment, the enlarged screw head 24 is sized to have a diameter thatmatches the diameter of the sleeve 30, measured from the outer surfacesof the sleeve body 32.

The nut and the drive nut are each internally threaded and haveidentical internal threads 33. The internal threads 33 are sized tothreadingly cooperate with the external threads 22 of the screw 20. Thisallows the nut, and the drive nut to be positioned over the screw 20.

The screw 20 also includes a frangible groove 28. The frangible groove28 is located at predescribed position on the threaded section of thescrew 20 and is machined to a diameter smaller than the minor diameterof the external threads 22. The frangible groove 28 serves as abreakneck that will fail in torsional shear and break away from theblind fastener 10 when a certain torsional load is achieved. Thisbreakneck function of the frangible groove 28 prevents over torquingand/or excessive upsetting of the sleeve during installation. In apreferred embodiment, the frangible groove 28 is machined at an axialposition on the screw 20 so that when the frangible groove 28 breaksaway the remaining portion of the screw 20 extending from head 24 willbe substantially flush with a top surface 43 of the nut head 44.

The sleeve 30 has a cylindrical shape and is made of a malleablematerial. The sleeve 30 is placed onto the screw 20 until the sleeve end34 abuts the screw head 24. The sleeve face 36 is designed to deformwhen the screw 20 is rotated and the nut 40 is drawn towards the sleeve30. A tapered nose 42 of the nut 40 presses against the internaldiameter of sleeve face 37 with such force that the sleeve body causesinternal diameter 37 to radially expand and ultimately buckle as itslides over tapered nose 42. Continued loading causes the sleeve body 32to increase in diameter and adjoin the blind inner surface 18 of sheet14, thereby securing sheets 12 and 14 together between the sleeve 30 andthe head 44 of the nut 40.

The nut 40 has a cylindrical shape and preferably resembles a flush headbolt. The nut 40 includes a nut body 41, the tapered nose 42 that islocated at one end of the nut body, and a nut head 44 located at an endopposite the tapered nose 42. The nut body 41 preferably has an outerdiameter substantially the same as the outer diameter of the sleeve body32. The tapered nose 42 projects inwardly and has a diameter that issmaller than the diameter of the nut body 41. The tapered nose 42 abutsthe sleeve internal diameter 37 when it is positioned on the screw 20.As shown in FIG. 2, the nut head 44 contains a driving recess 46 thatallows the drive nut 50 to be matingly engaged with the nut 40.

As shown in FIGS. 7a and 7 b, the driving recess 46 of the nut head 44comprises a plurality of indentations 48. The indentations 48 in thedriving recess 46 can be formed in any configuration that allows the nuthead 44 and drive nut 50 to be matingly engaged, and thereby preventrotation of the nut 40 and drive nut 50 during installation of the blindfastener 10. In a preferred embodiment, as shown in FIG. 7a, theindentations 48 are in a cross-slot configuration, and accordingly thedrive nut 50 must have protruding nibs 56 in a cross-slot configuration.The indentations 48 of the driving recess 46 can alternatively have asingle slot configuration, as shown in FIGS. 8a and 8 b, or any otherconfiguration such as the shape of a hexagon or square, as long as thenibs 56 of the drive nut 50 have a matching configuration.

As shown in FIGS. 9a and 9 b, the drive nut 50 preferably has the shapeof a traditional hexagon nut and has the same internal threads 33 as nut40. The drive nut 50 has an outer surface 52 for engagement by a drivingtool (not shown) that prevents rotation of the drive nut. The drive nut50 has a plurality of protruding nibs 56 that provide a positivemechanical engagement with the nut head 44. As discussed above, the nibs56 are configured to mate precisely with the indentations 48 whichcomprise the driving recess 46 of the nut head.

The nibs 56 are made of a non-deformable material, such that the nibs 56will not deform during installation of the blind fastener. As with theindentations 48 of the nut 40, the number of nibs 56 on the driving nut50 can vary and can be in many different geometrical shapes and forms.In a preferred embodiment, as shown in FIGS. 9a and 9 b, four nibs 56are present on the driving nut and each nib has a substantiallyrectangular shape with an engaging surface 57 and a driving surface 58.In FIG. 9a, the engaging surface 57 is angled relative to the drivingsurface 58 , while in FIG. 9b the engaging surface 57 is flat.Additionally, as shown in FIGS. 10a and 10 b, the drive nut 50 can beformed with two nibs 56, and with either an angled engaging surface, asshown in FIG. 10a, or with a flat engaging surface as shown in FIG. 10b.Preferably, the nibs 56 protrude from the drive nut face 54 comprising arectangular shape with a length equal to the distance between the outersurface 52 and the internal threads 33.

Prior to installing the blind fastener 10 into the sheets 12, 14, theblind fastener is assembled. Referring to FIGS. 1 to 3, the assemblyprocess comprises a series of steps which result in the sleeve 30, beingplaced over the screw and the nut 40 and the drive nut 50 being threadedonto the screw 20. First, as shown in FIG. 1, the sleeve 30 is placedover the external screw threads 22 until the sleeve end 34 is adjacentto the screw head 24. Next, the nut 40 is partially threaded onto thescrew 20 with the tapered nose 42 directed towards the sleeve face 36and the internal diameter 37. The nut 40 is preferably threaded onto thescrew until the internal threads 33 within the region of the nut head 44have not been completely threaded over the screw. Specifically, thedriving recess 46 of the nut would not be placed over screw at thispoint. Next, referring to FIG. 2, the drive nut 50 is positioned so thatthe protruding nibs 56 are aligned and physically engaged into thedriving recess 46 of the nut 40. At this point, the drive nut 50 and nut40 are in mating engagement wherein the engaging surfaces 57 and drivingsurfaces 58 of the nibs 56 are within the indentations 48 of the drivingrecess 46. Next, the mated drive nut 50 and nut 40 are rotated whichresults in the drive nut and nut being threaded onto the screw as asingle unit. Once the drive nut 50 has been partially threaded onto thescrew 20, the drive nut and nut are physically locked together. Next, asshown in FIG. 3, the drive nut 50 and nut 40 are threaded onto the screw20 until the tapered nose 42 of the nut is abutting the internaldiameter 37. Next, the nut 40 preferably undergoes a dimpling processwherein a small portion of an outer surface of the nut body 41 isphysically deformed against the screw 20 (not shown). The dimplingprocess results in a small portion of the nut 40 material beingdisplaced against the screw 20 to cause sufficient friction to preventloosening. The assembly process of the blind fastener 10 is thencomplete and the blind fastener is prepared for installation.

The installation of the assembled blind fastener 10 involves the blindfastener 10 being used to secure a plurality of sheets or panelstogether. As shown in FIG. 4, a preferred installation involves twosheets 12 and 14 being secured. The blind fastener 10 is inserted intothe sheets 12, 14 wherein the nut head 44 is received against theaccessible outer surface 16 of sheet 12, and the sleeve 30 extendsthrough the sheets 12, 14 and is adjacent to the inaccessible “blind”surface 18 of sheet 14.

An installation tool (not shown) is adapted to simultaneously havefitting engagement with both the drive nut 50 and the machined flats 26of the screw 20. The installation tool is placed onto the drive nut 50and creates an engagement that prevents the drive nut 50 from rotating.Accordingly, the nut 40 is also prevented from rotating because thedrive nut 50 and the nut 40 are in mating engagement. The installationtool also engages the machined flats 26 of the screw 20 and provides arotational torque on the screw 20.

As the installation tool rotates the screw 20 and holds the drive nut 50and nut 40 stationary, it is significant to note that there is nosmearing or scrapping of the surface 43 of the nut head 44 caused by thedrive nut 50. Because a positive mechanical engagement exists betweenthe nibs 56 of the drive nut and the mating driving recess 46 of the nutthere is also a complete elimination of any “jam nut effect” that existsin the previous blind fastener assemblies. The drive nut 50 isnon-deformable and as a result provides consistent and predictableresults. Unlike the previous blind fasteners which rely on forciblydeforming an annular ridge of the drive nut into the nut head, the drivenut 50 and nut head 44 will consistently engage as designed and notdeform when the installation load increases.

The increased installation load applied by the installation tool resultsin the sleeve 30 being drawn towards the tapered nose 42 of the nut andthe blind surface 18 of sheet 14. Referring to FIG. 5, because thesleeve 30 is made of a deformable material, as the internal diameter 37presses against the tapered nose 42 the sleeve body 32 and internaldiameter 37 begins to expand radially. As the sleeve body 32 adjoins theblind surface 18 of sheet 14 buckling continues on the upper portion ofinternal diameter 37.

At a predetermined torsional load, the sleeve 30 will have deformed andexpanded to a desired diameter and the break frangible groove 28 of thescrew 20 will fail in torsional shear and break away. As shown, in thepreferred embodiment the break frangible groove 28 is machined in anaxial position on the screw 20 so that just prior to when the frangiblegroove 28 breaks away, the remaining portion of the screw issubstantially flush with the surface 43 of the nut head 44. Moreover,the drive nut 50 is able to break away with the portion of the screw 20that breaks with the frangible groove 28 without any damage to thesurface 43 of the nut head 44 because the nibs 56 had not deformed intothe driving recess 46. As shown in FIG. 6, after installation iscomplete the sheets 12,14 are secured together between the nut head 44and the deformable sleeve 30.

FIG. 11 illustrates a second alternative embodiment drive nut 60 for usewith the blind bolt assembly of the present invention. Drive nut 60 isidentical to drive nut 50 with the exception of a smooth internal bore62. Considering drive nut 60 does not have internal threads the drivenut is held onto screw 22 by a retaining device 64. Device 64 can be anO-ring, a retaining ring or a plug which is placed over screw 62 againstthe back surface 66 of drive nut 60. Alternatively drive nut 66 could beheld onto pin 22 by applying an adhesive between smooth bore 62 and theexternal threads of screw 22.

FIG. 12 shows another alternative embodiment drive nut 70 which also hasa smooth internal bore 72 which has a tapered section 74 and is retainedon screw 22 by a tapered insert 76. Typically tapered insert 76 would bemade of nylon or any other suitable material. A drive nut with a smoothbore eliminates the need to thread the drive nut onto screw 22 forengagement of the nibs into the recesses of the nut. This reducesdramatically the installation time of the placement of the drive nutinto its proper position. Once the drive nut is slid into position, itmust be retained until the user begins the final installation process.As mentioned, devices such as a retaining ring, O-ring, plugs or taperedinserts that nest in a mating tapered hole in the backside of the drivenut can be used. The tapered insert provides a stronger resistance topull out because of the locking taper design and the higher the removalloads the tighter it becomes. The tapered polymer insert is thepreferred retaining device. As previously mentioned, alternatively adrop or two of any suitable adhesive can be placed into the smooth boreto bond the drive nut to the screw.

The assembly method of the drive nuts of FIGS. 11 and 12 begins with thesleeve being placed over the threads of the screw and set adjacent tothe head of the screw. The nut is then rotated onto the screw until itis adjacent the sleeve. The partial assembly of the screw, the sleeveand the nut is positioned for the dimpling process on the grip sectionof the nut. This process is a physical deformation of a small portion ofthe nut wall thickness that displaces nut material against the internalscrew to cause sufficient friction to prevent loosening. The drive nutwith the smooth bore is slid over the male threads of the screw and theprotruding nibs are aligned and physically engaged into the matingrecesses in the head of the nut. Once the drive nut is in position withthe mating recess of the nut, the retaining device is placed over thescrew adjacent the back surface of the drive nut. If an adhesive is usedin lieu of the retaining device, after the drive nut is placed over thescrew and the nibs engage the recesses in the nut, adhesive is appliedinto the bore to bond the drive nut to the screw.

Although the present invention has been described and illustrated inpreferred embodiments thereof, it is to be understood that changes andmodifications can be made therein which are within the full intendedscope of the invention as herein after claimed.

What is claimed is:
 1. A blind fastener comprising: a screw having aplurality of external threads and a head positioned at an end of thescrew; a sleeve having a deformable sleeve face positioned at the end ofthe screw adjacent the head; a nut having a plurality of internalthreads, an enlarged nut head positioned at an end of the nut, and adriving recess positioned within the enlarged nut head, wherein an endopposite the nut head is positioned on the screw adjacent to the sleeve;a drive nut having a smooth bore positioned on the screw adjacent thenut having an outer surface adapted for engagement by a driving tool anda plurality of protruding nibs extending from an end of the drive nutfor engaging the driving recess of the nut; and a device for engagingthe drive nut and the screw to hold the drive nut to the screw.
 2. Theblind fastener of claim 1 wherein the smooth bore of the drive nut hasan angled portion.
 3. The blind fastener according to claim 1 whereinthe device is an angled insert.
 4. The blind fastener according to claim1 wherein the device is an adhesive.
 5. The blind fastener according toclaim 1 wherein at least one of the nibs of the drive nut has arectangular configuration and the drive nut and the nut are made from anon-deformable material.
 6. A method for assembling a fastener systemcomprising the steps of: positioning a sleeve onto a screw; threading anut having a plurality of internal threads and a head having a drivingrecess onto the screw adjacent the sleeve; positioning a drive nuthaving a smooth bore and a plurality of protruding nibs extending froman end of the drive nut onto the nut so that the protruding nibs arealigned and matingly engaged into the driving recess of the nut; andplacing an engaging device adjacent the drive nut to retain the drivenut on the screw.
 7. The method of claim 6 further comprising the stepof dimpling an outer surface of the nut so that the nut is secured ontothe screw.
 8. The method of claim 6 wherein the engaging device is anangled insert which engages an angled portion of the smooth bore in thedrive nut.
 9. The method of claim 6 wherein the placing an engagingdevice comprises applying an adhesive between the smooth bore of thedrive nut and the screw.